DIGITAL PROJECTION DIGITAL PROJECTION RADIOGRAPHYRADIOGRAPHY

COMPUTED RADIOGRAPHYCOMPUTED RADIOGRAPHY

DIGITAL PROJECTION DIGITAL PROJECTION RADIOGRAPHYRADIOGRAPHY DEPENDS ON DEPENDS ON COMPUTER TECHNOLOGY TO COMPUTER TECHNOLOGY TO

PRODUCE DIGITAL PRODUCE DIGITAL RADIOGRAPHIC IMAGERADIOGRAPHIC IMAGE

DIGITAL PROJECTION RADIOGRAPHY

COMPUTED RADIOGRAPHY (CR) DIGITAL RADIOGRAPHY (DR)

DIGITAL RADIOGRAPHY DIGITAL RADIOGRAPHY

vsvs

COMPUTED RADIOGRAPHYCOMPUTED RADIOGRAPHY

DETECTORS

11011101

DR

ADC

X-RAYS

CR PLATE

11011101

CR

ADC

X-RAYS

SCANNER

COMPUTED RADIOGRAPHY COMPUTED RADIOGRAPHY (CR):(CR):

USES PHOTOSTIMULABLE PLATE (IMAGE USES PHOTOSTIMULABLE PLATE (IMAGE PLATE) PLATE)

INSTEAD OF FILM, AS THE IMAGE INSTEAD OF FILM, AS THE IMAGE RECEPTOR.RECEPTOR.

CRCR USES CASSETTE THAT LOOKS VERY USES CASSETTE THAT LOOKS VERY SIMILAR TO CONVENTIONAL SIMILAR TO CONVENTIONAL RADIOGRAPHIC CASSETTE. RADIOGRAPHIC CASSETTE.

CR PLATE !!!!!CR PLATE !!!!!

DOES NOT USE SCREENS OR DOES NOT USE SCREENS OR FILM ( CONVENTIONAL FILM)FILM ( CONVENTIONAL FILM)

CR PLATECR PLATE

CASETTE CONSTRUCTIONCASETTE CONSTRUCTION

►LIGHTWEIGHT ALUMINUMLIGHTWEIGHT ALUMINUM►PLASTICPLASTIC►STEEL FRAMESTEEL FRAME

FRONT PANEL MADE OF LOW ATTENUATION CARBON FIBER

CR CASSETTES ARE NOT CR CASSETTES ARE NOT LIGHT-TIGHTLIGHT-TIGHT

IMAGE PLATE IS NOT IMAGE PLATE IS NOT SENSITIVE TO LIGHTSENSITIVE TO LIGHT

CR CASSETTE IS CR CASSETTE IS PROTECTING IMAGE PLATE PROTECTING IMAGE PLATE

FROM DAMAGEFROM DAMAGE++

IS THE STABLE VEHICLE FOR IS THE STABLE VEHICLE FOR TRANSPORT AND TRANSPORT AND

PLACEMENT OF THE PLACEMENT OF THE CASSETTE UNDER THE CASSETTE UNDER THE

PATIENTPATIENT

BACK PANEL CONTAINS LEAD BACK PANEL CONTAINS LEAD FOIL TO PROTECT THE PLATE FOIL TO PROTECT THE PLATE

FROM FROM BACKSCATTER BACKSCATTER

BACK PANEL ALSO CONTAINS BACK PANEL ALSO CONTAINS CHIP TO RECORD PATIENT CHIP TO RECORD PATIENT

DEMOGRAPHIC INFORMATIONDEMOGRAPHIC INFORMATION

REMOTE OPERATOR PANELREMOTE OPERATOR PANEL

IMAGE PLATEIMAGE PLATE

APPROX. 1MM

CROSS-SECTION OF CR CROSS-SECTION OF CR PLATEPLATE

PROTECTIVE LAYER

PHOSPHOR LAYER

ANTI-HALO & REFLECTIVE LAYER

BASE

BACKING LAYER

BASEBASE

►PET- POLYETHYLENE TERAPHTALATEPET- POLYETHYLENE TERAPHTALATE

PHOSPHOR LAYERPHOSPHOR LAYER

►Ba FX: Eu Ba FX: Eu +2+2

PROTECTIVE LAYERPROTECTIVE LAYER

►FLUORINATED POLYMER MATERIALFLUORINATED POLYMER MATERIAL

PROTECTS PHOSPHOR LAYER

ANTI-HALO LAYER + REFLECTIVE ANTI-HALO LAYER + REFLECTIVE LAYERLAYER

►PREVENTS LASER FROM PASSING PREVENTS LASER FROM PASSING THROUGH.THROUGH.

►REFLECTED LIGHT FROM PHOSPHOR IS REFLECTED LIGHT FROM PHOSPHOR IS ALLOWED TO PASS.ALLOWED TO PASS.

BACKING LAYERBACKING LAYER

►PROTECTS THE BASE FROM DAMAGE.PROTECTS THE BASE FROM DAMAGE.

LEAD COATINGLEAD COATING

SCATTER

The simplest explanation for The simplest explanation for luminescence is that impurities in the luminescence is that impurities in the

crystal lattice are responsible for crystal lattice are responsible for luminescence. As the concentration of luminescence. As the concentration of impurity ions increase the greater the impurity ions increase the greater the

intensity of the luminescence. CR intensity of the luminescence. CR screens use barium fluorohalides doped screens use barium fluorohalides doped with europium (europium is the impurity with europium (europium is the impurity

in the crystal).in the crystal).

When phosphors are stimulated with x-When phosphors are stimulated with x-ray photon energy electron pair holes ray photon energy electron pair holes

are created. In effect, europium is raised are created. In effect, europium is raised to an excited state and upon to an excited state and upon

luminescence it is returned to its ground luminescence it is returned to its ground Eu2+ state. This mechanism holds for Eu2+ state. This mechanism holds for both spontaneous luminescence and both spontaneous luminescence and

photostimulated luminescencephotostimulated luminescence

The shifting of europium from its excited The shifting of europium from its excited state back to its ground state for both state back to its ground state for both

spontaneous and photostimulated spontaneous and photostimulated luminescence is about 0.6 - 0.8 luminescence is about 0.6 - 0.8

microseconds. With screen-film imaging microseconds. With screen-film imaging these crystals spontaneously these crystals spontaneously

luminescence to expose a film, but with luminescence to expose a film, but with CR imaging the luminescence occurs, CR imaging the luminescence occurs, then there is also photoluminescence then there is also photoluminescence

that occurs when the screen is that occurs when the screen is stimulated by a narrow beam of infrared stimulated by a narrow beam of infrared

light.light.

The holes or vacancies in the lattice are The holes or vacancies in the lattice are portions of the lattice normally occupied portions of the lattice normally occupied

by halogens (fluoride, bromide, or by halogens (fluoride, bromide, or iodine). These vacancies will trap free iodine). These vacancies will trap free

electrons when irradiated and are called electrons when irradiated and are called FarbzentrenFarbzentren centers or centers or F-centersF-centers..

When the photostimulable plate is When the photostimulable plate is exposed to high frequency light, usually exposed to high frequency light, usually

from a helium laser, the electrons in from a helium laser, the electrons in these F-centers are liberated and cause these F-centers are liberated and cause

luminescence at readout.luminescence at readout.

THE LATENT IMAGE WILL THE LATENT IMAGE WILL REMAIN STORED FOR 24 REMAIN STORED FOR 24

HOURS.HOURS.

IT WILL FADE THROUGH IT WILL FADE THROUGH PHOSPHORESCENCEPHOSPHORESCENCE

FADINGFADING

► 25% OF STORED 25% OF STORED ENERGYENERGY

► WITHIN 8 HOURSWITHIN 8 HOURS

CR AFTER EXPOSURE IS CR AFTER EXPOSURE IS INSERTED INTO INSERTED INTO CR SCANNERCR SCANNER

CR PLATE

CR SCANNER/READER

THE SCANNER SCANS THE THE SCANNER SCANS THE IMAGE PLATE WITH LASER IMAGE PLATE WITH LASER

LIGHT AND READS THE LIGHT AND READS THE LATENT IMAGE FROM THE LATENT IMAGE FROM THE

PHOSPHORPHOSPHOR

READOUTREADOUT

LASER LIGHTLASER LIGHT

HELIUM-NEON (633 nm) HELIUM-NEON (633 nm) LASER BEAM SWEEPS THE LASER BEAM SWEEPS THE PLATE IN RASTER FASHIONPLATE IN RASTER FASHION

RASTER RASTER

PM TUBE

AMPLIFIER ADC

LASER

LIGHTGATE

SWEEPING OF THE LASER SWEEPING OF THE LASER ACROSS THE PLATEACROSS THE PLATE

►FAST SCAN DIRECTIONFAST SCAN DIRECTION►SCAN DIRECTIONSCAN DIRECTION►LASER SCAN DIRECTIONLASER SCAN DIRECTION

PLATE MOVEMENT IN THE PLATE MOVEMENT IN THE SCANNERSCANNER

►SLOW SCAN DIRECTIONSLOW SCAN DIRECTION►SUB-SCAN DIRECTIONSUB-SCAN DIRECTION►PLATE SCAN DIRECTIONPLATE SCAN DIRECTION

THE SPEED OF THE THE SPEED OF THE SCANNING LASER BEAM IS SCANNING LASER BEAM IS

ADJUSTED TO THE ADJUSTED TO THE LUMINESCENT SIGNALLUMINESCENT SIGNAL

PLATE & F-CENTERS

LASER 633 nm

PHOTOSTIMULABLE LUMINESCENCE

390-400 nm

LASER LASER SPOT SIZE - LASER LASER SPOT SIZE - 100 MICROMETERS100 MICROMETERS

PIXEL SIZE - 100 PIXEL SIZE - 100 MICROMETERSMICROMETERS

P.M. TUBE DETECTION P.M. TUBE DETECTION SENSITIVITY MATCHED TO SENSITIVITY MATCHED TO

BLUE-PURPLE BLUE-PURPLE PSLPSL (390-400 (390-400 nm)nm)

AFTER SCANNING THE CR AFTER SCANNING THE CR PLATE NEED TO BE CLEARED PLATE NEED TO BE CLEARED

FROM RESIDUAL SIGNALFROM RESIDUAL SIGNAL

PLATE EXPOSED TO HIGH PLATE EXPOSED TO HIGH INTENSITY SODIUM VAPOR INTENSITY SODIUM VAPOR

OR OR FLUORESCENT LIGHT FLUORESCENT LIGHT

Typical image plate can be Typical image plate can be reused reused thousands of timesthousands of times

IMAGE DISPLAYIMAGE DISPLAY

IMAGE CHECK-INDEX???IMAGE CHECK-INDEX???

IMAGE MANIPULATION-IMAGE MANIPULATION-WINDOWINGWINDOWING

PICTURE DESTINATION -PACSPICTURE DESTINATION -PACS

PACSPACS

CR CHARACTERISTIC CURVECR CHARACTERISTIC CURVE

►VERY WIDE LATITUDEVERY WIDE LATITUDE

CR SYSTEMSCR SYSTEMS

►LESS RADIOGRAPH REPEATSLESS RADIOGRAPH REPEATS

CHARACTERISTIC CURVECHARACTERISTIC CURVE

LATITTUDE OF CR

LATITTUDE OF FILM

IMAGE CAN BE SALVAGED WITH IMAGE CAN BE SALVAGED WITH CRCR

►500% OVEREXPOSURE500% OVEREXPOSURE

►80% UNDEREXPOSURE80% UNDEREXPOSURE

USE ADEQUATE KVP

HARD COPY GENERATED IN HARD COPY GENERATED IN LASER PRINTERLASER PRINTER

CR SYSTEM EFFICIENCY CR SYSTEM EFFICIENCY CHARACTERISTICCHARACTERISTIC

►QDE- QUANTUM DETECTION QDE- QUANTUM DETECTION EFFICIENCYEFFICIENCY

NO NEED FOR SCREENS

QDE:QDE:

THE MEASURE OF THE EFFICIENCY OF THE MEASURE OF THE EFFICIENCY OF CR SYSTEM TO CONVERT REMNANT X-CR SYSTEM TO CONVERT REMNANT X-

RAYS TO USEFUL IMAGE SIGNALRAYS TO USEFUL IMAGE SIGNAL

QDEQDE

PATIENT DOSE PATIENT DOSE

DIGITAL RADIOGRAPHYDIGITAL RADIOGRAPHY

ELECTRONIC DETECTORSELECTRONIC DETECTORS

► INDIRECT TECHNIQUE CLASSINDIRECT TECHNIQUE CLASS►DIRECT TECHNIQUE CLASSDIRECT TECHNIQUE CLASS

INDIRECT TECHNIQUEINDIRECT TECHNIQUE

► INDIRECT CONVERSION FLAT PANEL INDIRECT CONVERSION FLAT PANEL DETECTORSDETECTORS

► INDIRECT CONVERSION CHARGED INDIRECT CONVERSION CHARGED COUPLE DEVICE DETECTORSCOUPLE DEVICE DETECTORS

INDIRECT CONVERSION FLAT INDIRECT CONVERSION FLAT PANEL DETECTORSPANEL DETECTORS

►USE THIN LAYERS OF SILICON USE THIN LAYERS OF SILICON COMBINED WITH THE ARRAYS OF COMBINED WITH THE ARRAYS OF PHOTODIODES. P.D. IS COATED PHOTODIODES. P.D. IS COATED WITH CESIUM IODIDE OR RARE WITH CESIUM IODIDE OR RARE EARTH MATERIAL- WHEN STRUCK BY EARTH MATERIAL- WHEN STRUCK BY REMNANT X-RAYS THEY EMIT LIGHT. REMNANT X-RAYS THEY EMIT LIGHT.

ADVANTAGE: HIGH QDEDISADVANTAGE: LIGHT DIVERGENCE

PHOTODIODEPHOTODIODE

INDIRECT CONVERSION INDIRECT CONVERSION CHARGE COUPLED DEVICE CHARGE COUPLED DEVICE

DETECTORSDETECTORS►USE CCD ARRAYS TO RECORD THE USE CCD ARRAYS TO RECORD THE

VISIBLE LIGHT EMITTED BY A VISIBLE LIGHT EMITTED BY A SCINTILLATION CRYSTAL THAT HAS SCINTILLATION CRYSTAL THAT HAS ABSORBED THE ENERGY. AN OPTICAL ABSORBED THE ENERGY. AN OPTICAL COUPLING SYSTEM DEMAGNIFIES THIS COUPLING SYSTEM DEMAGNIFIES THIS LIGHT AND SENDS IT TO THE CCD LIGHT AND SENDS IT TO THE CCD ARRAY.ARRAY.

OPTICAL COUPLINGOPTICAL COUPLING

CCDCCD

DIRECT TECHNIQUEDIRECT TECHNIQUE

►DIRECT CONVERSION FLAT PANEL DIRECT CONVERSION FLAT PANEL DETECTORSDETECTORS

DIRECT CONVERSION FLAT DIRECT CONVERSION FLAT PANEL DETECTORSPANEL DETECTORS

► USE AN AMORPHOUS SELENIUM COATED THIN USE AN AMORPHOUS SELENIUM COATED THIN FILM TRANSISTOR ARRAY THAT DIRECTLY FILM TRANSISTOR ARRAY THAT DIRECTLY CONVERTS X-RAY ENERGY INTO ELECTRICAL CONVERTS X-RAY ENERGY INTO ELECTRICAL SIGNAL. REMNANT X-RAYS ARE ABSORBED IN SIGNAL. REMNANT X-RAYS ARE ABSORBED IN THE SELENIUM WHERE THEY FORM ELECTRON-THE SELENIUM WHERE THEY FORM ELECTRON-

HOLES. CAPACITORS COLLECT THE CHARGE.HOLES. CAPACITORS COLLECT THE CHARGE.

ADVANTAGE: NO LIGHT DIVERGENCE

READY - The 17"x17" amorphous selenium-based sensor is electrically sensitized and readied for exposure.

         

                                                                  

EXPOSE - Incident X-ray photons are converted into electron-hole pairs. A transverse electric field separates the electrons and holes and creates a charge image precisely corresponding to the X-ray image.

READOUT - The microplasma line scanner sweeps across the sensor in less than 2 seconds causing readout of the charge image and sensor reset.

DR vs CR COMPARISONDR vs CR COMPARISON

► IMMEDIATE REDOUTIMMEDIATE REDOUT► CASSETTE FREE CASSETTE FREE

OPERATIONOPERATION► GOOD FOR HIGH GOOD FOR HIGH

VOLUME VOLUME RADIOGRAPHYRADIOGRAPHY

► CAN BE USED FOR CAN BE USED FOR MAMMOGRAPHYMAMMOGRAPHY

► DETECTORS CAN BE DETECTORS CAN BE RE-EXPOSED RE-EXPOSED IMMEDIATELYIMMEDIATELY

► MORE EXPENSIVEMORE EXPENSIVE► CAN NOT BE USED IN CAN NOT BE USED IN

PORTABLE PORTABLE RADIOGRAPHY??????RADIOGRAPHY??????

► NOT COMPATIBLE WITH NOT COMPATIBLE WITH EXISTING TABLESEXISTING TABLES

ADVANTAGE DISADVANTAGE

DR SYSTEM

PORTABLE????PORTABLE????

PORTABLE CT???!!PORTABLE CT???!!

MONITORS IN DRMONITORS IN DR

► 1K1K

► 2K2K

► 4K4K

► 1,000 X 1,000 PIXELS1,000 X 1,000 PIXELS

► 2,000 X 2,000 PIXELS2,000 X 2,000 PIXELS

► 4,000 X 4,000 PIXELS4,000 X 4,000 PIXELS

4K MONITORS USED IN MAMMOGRAPHY AND CHEST RADIOGRAPHY

DR TERMS TO KNOWDR TERMS TO KNOW

► PIXEL PIXEL ► VOXELVOXEL► SPATIAL RESOLUTIONSPATIAL RESOLUTION► DYNAMIC RANGEDYNAMIC RANGE► CONTRAST RESOLUTIONCONTRAST RESOLUTION► IMAGE NOISEIMAGE NOISE

PIXELPIXEL

VOXELVOXEL.

                                                                                                                  

The formation